The limits the maximum queue size to 255, which I think is ok for the
forseable future.
sizeof(uORB::DeviceNode) is reduces from 128 to 112 on NuttX, and with
~80 instances, this saves over 1KB of RAM.
uORB was refactored in order to support the MuORB changes required
for QURT. Those changes wil be added in a subsequent commit.
The files are split out by posix and nuttx so the changes are visible.
When this has been tested, the files can be re-merged and re-tested.
Signed-off-by: Mark Charlebois <charlebm@gmail.com>